1. Field of the Invention
The present invention relates to a syntactic analysis apparatus which performs a syntactic analysis of an input sentence so as to produce a syntactic tree of the input sentence, and more specifically, to the syntactic analysis apparatus which is particularly effective for producing the syntactic tree when the input sentence includes a syntactic error.
2. Description of the Prior Art
In a conventional syntactic analysis apparatus, when an input sentence includes a syntactic error, a result is, for example, failing in a syntactic analysis of the input sentence due to failure in applying a syntax analyzing rule, or outputting syntactic subtrees of the input sentence obtained up to the failure in the syntactic analysis of the input sentence, or dividing the input sentence into units each syntactically analyzable so as to reanalyze the syntax of the input sentence. However, any of these results does not accomplish a final object of the syntactic analysis apparatus, that is, generating a correct syntactic tree of the entire input sentence.
On the other hand, there have also been available another syntax analyzing method, wherein a syntactic analysis of an input sentence is performed such that a simple error in a syntactic attribute relationship is allowed by removing an attribute check function from a syntax analyzing rule.
In general, the syntactic analysis checks appropriateness with respect to a combination of parts of speech or other grammatical categories of a portion of the input sentence and with respect to an attribute relationship therebetween, and produces a syntactic subtree corresponding to a syntax analyzing rule which is determined applicable based on the above-noted appropriateness, so as to finally generate a syntactic tree of the entire input sentence. Accordingly, as appreciated, when there are plural combinations of the syntax analyzing rules which are determined applicable, a plurality of the syntactic trees are produced for one input sentence.
Accordingly, when a condition on the appropriateness relative to the attribute relationship is relaxed in the syntax analyzing rule as in the foregoing prior art, a syntax analyzing rule which should not be actually applied is likely to be determined applicable. As a result, a number of the syntactic trees including wrong syntactic trees are generated relative to one input sentence.